The （60-x）Bi2O3-xGeO2-30B2O3-10ZnO （x=5, 10, 20, 30 molar percent） glasses doped with Er 3+ and Er 3+ /Yb 3+ were fabricated using the melting method. The thermal stability of the glasses was studied with their DTA curves. The results show that the difference between the glass transition temperature and the crystallization onset temperature increases with the increase of GeO2 content, indicating that the thermal stability of the glass has become better. The absorption spectra were recorded and the stimulated emission cross sections were calculated using the McCumber theory. The Ω2, Ω4, and Ω6 parameters,the transition probability, the radiative lifetime, and the fluorescence branch ratio of Er 3+ for optical transition were calculated from their absorption spectra in terms of reduced matrix U （t） （λ=2, 4, 6） character for optical transitions. The infrared emission of Er 3+ was measured upon excitation with 970 nm light and the full width at half-maximum （FWHM） was estimated from the emission spectra. The pumping efficiency and the intensity of the emission at the 1.54 μm band of Er3+ were enhanced considerably by co-doping Yb 3+ .
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